Fix typo "vlue" to "value" in XML comment

* fix XINFO

* fix XGROUP ("-" => "0")

* fix XREAD/XREADGROUP ("-" => "0")

* fix XADD: entry-id must **follow** MAXLEN (fix #982)

lib updates (in particular, see https://github.com/aspnet/KestrelHttpServer/issues/2694#issuecomment-420347853)

* make transaction inner tasks use RunContinuationsAsynchronously (for discussion, see issue #943); detect RunContinuationsAsynchronously in ResultBox completion, and set directly rather than deferred